When the U.S. Attorney dropped its fraud case against Lance Armstrong earlier this year, the response from the Texan was a muted let’s-just-get-on-with-our–lives statement. There was no jubilation after the multi-year, multi-million dollar investigation collapsed, because the Armstrong camp knew that the U.S Anti-Doping Agency (USADA) was lurking. USADA, “the independent anti-doping agency for Olympic related sport in the United States” was tailgating witnesses and evidence from the U.S. Attorney’s office.

USADA has become Armstrong’s new Ahab. USADA is charging him with basically leading a doping gang, dating to the mid-1990s, that allowed him to roll up seven Tour de France wins. Several doctors and trainers on Armstrong teams, such as the U.S. Postal Service and Radio Shack, have also been targeted, including team manager Johan Bruyneel. Armstrong called the allegations a “witch hunt,” and reasserted his innocence. “I have never doped, and, unlike many of my accusers, I have competed as an endurance athlete for 25 years with no spike in performance, passed more than 500 drug tests and never failed one,” he said in a statement. That’s a reference to the unexpected, and ultimately doping-aided victories that some of his accusers have achieved, as opposed to his consistent winning record. “Any fair consideration of these allegations has and will continue to vindicate me,” said. The clear implication is that he obviously doesn’t consider USADA to be capable of fairness—which the agency denies.

One immediate consequence is that Armstrong is barred from competing as a triathlete in sanctioned events; he already won an event and was scheduled to compete in an Ironman race in France. There’s a presumption of innocence, according to USADA, but it does not extend to participation.

This is not a criminal case, although USADA will seek to prove Armstrong is a cheat by using some of the evidence that the U.S. Attorney had available— evidence that the U.S. Attorney decided couldn’t win a criminal case for fraud. That’s significant, because to prove the fraud case the government essentially had to prove that Armstrong was doping. The government dropped the case despite testimony from former Armstrong confederates such as Tyler Hamilton and Floyd Landis, who have said they used banned substances and said Armstrong did likewise. USADA also says it has blood samples from 2009 and 2010 that are “fully consistent with blood manipulation including EPO use and/or blood transfusions,” although these same samples were found to be clean by cycling authorities when first tested. Armstrong’s attorney, Robert Luskin, has demanded the agency provide the names of witnesses, as well as the blood tests, according to USA Today.

Armstrong’s biggest problem could be that USADA has a different standard of culpability than does the U.S. Constitution. Instead of “beyond a reasonable doubt”, USADA’s standard of guilt is “clear and concise” evidence, in the judgment of an independent arbitration panel that would be handed the case. It’s a potentially lower bar, which is why Armstrong has criticized USADA’s “star-chamber practices, and its decision to punish first and adjudicate later.” USADA’s arbitration panel, for instance, can credit witnesses that the U.S. Attorney decided not to put on the witness stand.

Armstrong has until June 22 to answer the charges and present any evidence in his favor. If he chooses not to do so—and there are indications he may not—USADA will hand the case off to its review board, which will then decide whether there “sufficient evidence of doping to proceed with the adjudication process,” that is, file formal charges. Then it’s up to the arbitration panel. If found guilty, Armstrong could be stripped of all his titles, not to mention having his legacy of work in his cancer charity, Livestrong, irrevocably tarnished. But he will not be out of legal options in the U.S., including going back to court. He can also appeal to the Court of Arbitration for Sport in Switzerland. Either way, Armstrong has a couple more mountains to climb. It’s a good thing he thrives on challenge.